Hi,

This patch intends to implement a new feature discussed in thread
http://sourceware.org/ml/gdb-patches/2012-06/msg00271.html. With this patch,
stub can return host gdb with zlib-compressed object which consumes less
space and communication overhead compared to its uncompressed format.

A minor change from our discussion is that "compressedXML" is replaced with
"compressedXfer" which I think is more representative because we may
transfer something other than XML file.

Please help to review and comment this patch. Thanks in advance.

BR,
Terry

gdb/doc/ChangeLog:

2012-08-07  Terry Guo  <terry.guo@arm.com>

	* gdb.texinfo (General Query Packets): Document new 
	compressedXfer stub feature.
	(General Query Packets): Document new zread packets.


gdb/ChangeLog:

2012-08-07  Terry Guo  <terry.guo@arm.com>

	* defs.h (gdb_zlib_error): Declare.
	* utils.c (gdb_zlib_error): New function.
	* remote.c (struct remote_state): New field has_cmprs_xfer.
	(enum packet_cmprs_xfer): New enum.
	(struct packet_config): New field xfer_status.
	(add_packet_config_cmd): Initialize the field xfer_status.
	(remote_packet_is_cmprs_xfer): New function.
	(remote_compressed_xfer_feature): New function.
	(remote_protocol_features): New feature compressedXfer.
	(remote_read_qxfer): Try zread and fallback to plain read when
	fails.
	* target.c (target_decompress_buf): New function.
	(target_read_stralloc): Decompress buffer first if any.
	* target.h (remote_packet_is_cmprs_xfer): Declare.